Thermal effects in the size distribution of SiC nanodots on Si(111)

Abstract

We have used scanning tunneling microscopy (STM), Auger electron spectroscopy (AES) and X-ray Photoelectron spectroscopy (XPS) to investigate the formation of nanoscopic structures on Si(111), from wafers with a high bulk C concentration. The samples were prepared by long time thermal annealing of the silicon samples, followed by a high temperature flash in ultrahigh vacuum. An increased surface C concentration is induced by segregation from the bulk. The surface is found to roughen on the nanososcopic length scale, exhibiting a random distribution of nanostructures. The height range of the structures varies between 2 and 20 nm. The size distribution is strongly dependent on the low-temperature preparation conditions. Ex-situ XPS measurements reveal the formation of SiC bonds, thus confirming the nanodots are formed by a surface recombination of SiC.